1. Field of the Invention
The present invention concerns an improved process for the disposal of waste and the conversion of hydrothermally labile chemical compounds to species which are environmentally acceptable or are more amenable to further degradation by conventional disposal systems to produce environmentally acceptable products. Specifically, the waste materials are reacted with specific aqueous inorganic salts at elevated temperature and pressure, and when necessary the reaction product is optionally further degraded in a conventional biological sewage system.
2. Description of Related Art
Present waste treatment and disposal techniques involve land fill, disposal at sea, combustion in some form, or combinations thereof. General waste treatment and disposal techniques are well known in the art. See for example, N. L. Nemerow in "Industrial Wastes" in Kirk-Othmer: Encyclopedia of Chemical Technology, 3rd ed., Vol. 24, pp. 227-256, published in 1984; D. A. Tillman in "Fuels from Waste" in Kirk-Othmer: Encyclopedia of Chemical Technology, 3rd ed., Vol. 11, pp. 393-410, published in 1980; and B. R. Crocker et al, in "Incinerators" in Kirk-Othmer: Encyclopedia of Chemical Technology, 3rd ed., Vol. 13, pp. 182-206, published in 1981. Waste material includes, but is not limited to, military waste, ordnance waste, dairy products waste, pharmaceutical manufacturing waste, chemical process waste, chemical agents, chemical by-products, agricultural waste, combinations thereof and the like. In particular, the treatment and safe disposal of hazardous military waste has become a project of urgent importance because the scale of disposal has enlarged to proportions far beyond that of only a few years ago.
Current disposal practices most often used are combustion and incineration-based. However, despite significant advances in incineration technology, there is increasing public apprehension and resistance to its present and future use. See, for example, David J. Hanson, in Chemical and Engineering News, pp. 7-14, published Mar. 29, 1993.
Some art of interest is as follows:
D. V. Moses, et al. in U.S. Pat. No. 2,690,425 disclose a process for the disposal of industrial wastes of an organic nature by contact with a solid catalyst of manganese-zinc-chromium at a temperature of 100.degree.-350.degree. C. and a pressure of between 200 and 2400 psi. PA1 C. M. Saul in U.S. Pat. No. 3,207,572 disclose a process for the wet combustion of waste liquors containing combustible organic materials. Oxygen or air is always present. PA1 J. W. Monroe, et al. in U.S. Pat. No. 3,312,231 disclose an apparatus and method for the removal and reclamation of solid propellant rocket motor cases. No inorganic salt catalyst is used. Also refer to L. B. Scott in U.S. Pat. No. 3,440,096. PA1 M. J. Mcintosh in U.S. Pat. No. 3,451,789 disclose a process for removing oxidizers from a solid propellant. The process involves the mechanical reduction of the propellant to small crystals followed by contact with leach water. PA1 W. M. Fassell, et al. in U.S. Pat. No. 3,870,631 disclose an apparatus and method for oxidation of organic matter at elevated temperatures and pressures in the presence of oxygen. No salt catalyst is described. PA1 C. A. Hoffman in U.S. Pat. No. 3,876,497 discloses a process for wet air oxidation where the organic materials present in paper mill sludges are converted into environmentally acceptable oxidation products. PA1 J. E. Morgan in U.S. Pat. No. 3,920,506 discloses a process for the wet combustion of waste liquors at elevated temperature and elevated pressure in the presence of an oxygenating gas. PA1 W. T. Nelson et al. in U.S. Pat. No. 4,000,068 disclose a process for the purification of organic compound containing polluted water using a water soluble copper salt catalyst in the presence of oxidizing conditions. PA1 J. W. Mandoki in U.S. Pat. No. 4,005,762 discloses aqueous hydrolyses and depolymerization of condensation polymers at a temperature of between 200.degree. and 300.degree. C. and elevated pressure of at least 15 atmospheres. PA1 J. Kreuter in U.S. Pat. No. 4,013,552 discloses a method of accelerating decomposition of liquid or solid sewage waste by irradiation using ultrasonic energy. PA1 L. A. Pradt in U.S. Pat. No. 4,013,560 discloses a process for wet oxidation of aqueous liquors at elevated temperatures and elevated pressures in the presence of an oxidizing gas to produce mechanical power. PA1 J. C. Hoffsommer, et al. in U.S. Pat. No. 4,018,676 disclose a process for the removal of explosive materials from water by chemical interaction using strongly basic ion exchange resins. PA1 C. C. Andrews, et al. in U.S. Pat. No. 4,038,116 disclose a method for treating an aqueous solution of aromatic explosives. An additive such as acetone or hydrogen peroxide is added to an aqueous solution of organic aromatic explosives, which mixture is exposed to ultraviolet light. PA1 R. Thiel et al. in U.S. Pat. No. 4,141,829 disclose a process for the oxidation of organic substances in an aqueous solution using molecular oxygen at elevated temperature and elevated pressures. PA1 R. P. McCorquodale in U.S. Pat. No. 4,604,215 discloses a process for wet oxidizing an aqueous suspension of organic material at elevated temperature and pressure in the presence of specific inorganic catalysts. PA1 K. Mitsui, et al., in U.S. Pat. No. 4,751,005 disclose the treatment of waste water by subjecting it to wet oxidation in the liquid phase in the presence of a catalyst containing a composite oxide of at least two metals selected from the group consisting of Ti, Si and Zn, and at least one metal selected from the group consisting of Mn, Fe, Co, Ni, W, Cu, Ce, Ag, Pt, Pd, Rh, Ru and In, or a compound of the one metal described above. PA1 D. C. Sayles in U.S. Pat. No. 4,758,387 discloses a process for the decomposition of propellants using water and a detergent at elevated temperatures and pressures. PA1 W. Gresser, et al. in U.S. Pat. No. 5,011,614 disclose a process for effecting thermal decomposition of explosive nitric acid esters in wastewater. In this process, the dissolved esters are exposed to a temperature of between 150.degree. and 300.degree. C. under pressure above the boiling point of the waste water. PA1 The Zimpro process utilizes a wet air oxidation as described in product brochures obtained from Zimpro, Inc., Environmental Control Systems, Rothschild, Wis. 54474. PA1 M. Roth in U.S. Pat. No. 4,231,822 discloses a non-polluting process for desensitizing explosives by contact with a reductant (e.g., oxalic acid, formic acid, glucose, etc.) at elevated temperature. PA1 A. S. Tompa, et al. in U.S. Pat. No. 4,098,627 disclose the solvolytic degradation of pyrotechnic materials containing crosslinked polymers. The process uses a temperature of 50.degree. to 160.degree. C. in a liquid medium having an active hydrogen. No salt compounds as catalysts are disclosed. PA1 M. Modell in U.S. Pat. No. 4,338,199 discloses the supercritical water oxidation (SCWO) of organic materials to obtain useful energy and/or resultant materials using a temperature of at least 377.degree. C. and a pressure of at least 220 atmospheres. In this process, the water present is always in the gas phase above the critical temperature of water. Further, an additional oxidant (e.g. oxygen, etc.) is always present. PA1 The Sterling Drug Co. in British Pat. No. 706,586 disclose a process using between 450.degree. F. and the critical temperature of water, preferably between 480.degree. and 625.degree. F. at elevated pressure for the destructive oxidation of organic materials in aqueous media. No catalyst is present. PA1 A. H. Lamberton, et al. in the Journal of the Chemical Society pp. 1650-1656 (1949) disclose the decomposition of nitramines in water at temperatures below 70.degree. C. at pH ranges of 3 to 8 in the absence of added inorganic salts. Inorganic acid, inorganic base and formaldehyde were found to catalyze the decomposition. PA1 J. C. Hoffsommer, et al. in the Journal of Physical Chemistry, Vol. 81 (#5), pp. 380-385 (1977) disclose the kinetic and activation parameters for aqueous alkaline homogeneous hydrolysis of 1,3,5-triaza-1,3,5-trinitrocyclohexane (RDX). PA1 (a) conveying an aqueous solution or slurry of the waste material into a reaction zone capable of safely withstanding the temperatures and pressures of the hydrothermal decomposition; PA1 (b) reacting the waste material in the reaction zone with an aqueous composition comprising silica or one or more alkali metal or alkaline earth metal silicates, borates, phosphates, biphosphates, or trisubstitutedphosphates, at between about 200.degree. C. and 500.degree. C. and at a pressure between about 20 and 500 atmospheres for between about 0.01 and 10 minutes; PA1 (c) producing compounds which are environmentally acceptable or are amenable to further degradation by conventional disposal systems; and PA1 (d) optionally degrading further the compounds of step (c) by reaction in a conventional disposal system. Some water is always present as a liquid. PA1 in step (b) the reaction temperature is between about 250.degree. and 400.degree. C. and the pressure is between about 100 and 300 atmospheres. Some water as a liquid is always present. PA1 lithium silicate, sodium silicate, potassium silicate, rubidium silicate, cesium silicate, lithium borate, sodium borate, potassium borate, rubidium borate, cesium borate, lithium phosphate, sodium phosphate, potassium phosphate, rubidium phosphate, cesium phosphate, lithium biphosphate, potassium biphosphate, rubidium biphosphate, cesium biphosphate, trilithium phosphate, trisodium phosphate, tripotassium phosphate, trirubidium triphosphate, tricesium phosphate, PA1 magnesium silicate, calcium silicate, barium silicate, strontium silicate, magnesium borate, calcium borate, barium borate, strontium borate, magnesium phosphate, calcium phosphate, barium phosphate, strontium phosphate, magnesium biphosphate, calcium biphosphate, barium biphosphate, strontium biphosphate, trimagnesium phosphate, tricalcium phosphate, tribarium phosphate, tristrontium phosphate or combinations thereof. More preferably, the salt is independently selected from sodium borate, potassium borate, sodium silicate, potassium silicate, trisodium phosphate, tripotassium phosphate or combinations thereof. PA1 the waste material is selected from ordnance, ordnance waste or ordnance formation waste water; and PA1 in step (b) the reaction temperature is between about 200.degree. and 373.degree. C. and below the critical temperature of water, and the reaction time is between 0.01 and 5 minutes and, the salts are present in the aqueous composition in a concentration of between about 1 and 40 percent by weight of the salt/water present. More preferably the inorganic salts are independently selected from sodium borate, potassium borate, sodium silicate, potassium silicate or combinations thereof.
None of these references individually or separately teach or suggest the present invention.
All patents, patent applications, articles, references, publications, standards and the like cited in this application are incorporated herein by reference in their entirety.
There is therefore a strong need for alternative methods of decomposition and disposal of waste to the presently used incineration methods. What is needed is a process which circumvents combustion, the need to introduce air, oxygen or other oxidants, and the need to introduce promoters which are often themselves environmentally unsuitable. Further, the process should at the same time have the flexibility to handle a wide range of waste materials with high degrees of volume, reliability and safety. Further, control of the species in the overall product stream should be possible, in that the products can either be discharged directly to the environment or can be readily treated effectively and efficiently by conventional secondary waste treatment processes and facilities.
The operational and commercial value of the present invention is that it provides a process to decompose waste material safely to environmentally acceptable products at milder conditions than are currently available. Further, it provides a framework for one to be able to control the rate of hydrothermal decomposition by judicious choice of salt(s), waste material, concentrations, temperature and pressure. That is to say, the hydrothermal decomposition is accelerated using the catalysts to practical and economically useful rates, while at the same time the rate is safely controlled within conventional equipment so that it is not so fast as to be uncontrolled or hazardous. The present invention provides a process to accomplish these results.